[opendtv] Re: (No Date: Tue, 28 Sep 2004 10:30:37 -0400

  • From: Ron Economos <k6mpg@xxxxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Sat, 16 Oct 2004 04:17:18 -0700

Interesting. Like John Willkie, I wonder how recent this data point is.
It would be sad to forever condemn ATSC flexible resolutions because
of some ancient out of circulation receiver(s).

As it turns out, 704x480 is actually a better choice for NTSC simulcast
than 720x480. The NTSC active line length of 52.6555 microsecs works
out to about 711 active pixels with ITU-R.BT601 sampling. The often
sharp transition from active video to black in the right hand edge column
of macroblocks in a 720x480 raster tends to use a lot of bits in an area
of the image that hardly anyone sees due to overscan.

Of course, the correct resolution for NTSC simulcast is 480x480 since
it more or less replicates the 4.2 MHz luma bandwidth of OTA NTSC
(or you can hedge it a little and use 528x480 like digital cable does or
544x480 like DBS).

An AVSForum member in St. Paul MN. has posted that his local DTV
station is actually sending 480x480 video bitstreams. I've asked him to
send me a capture of the stations Transport Stream.

Ron

Mark Schubin wrote:

> >
> >
> >I've seen you post this a few times. Please cite a specific MPEG-2 decoder
> >chip used in ATSC recievers that does not support 1440x1080, 1280x1080,
> >720x480, 544x480, 480x480 and 352x480.
> >
> Alas, the ATTC web site (like the ATTC) is no more.  It used to have
> posted the results of testing it performed on behalf of ATSC T3/S6 to
> see whether any existing ATSC receivers could not deal with 720 x 480.
>  They tried various modes (4:3 and 16:9, different frame rates).  Of
> seven receivers tested, one was unable to properly deal with 720 x 480
> in one mode, and another was unable to do it in a different mode.  So,
> yes, there's a problem.
>
> As a T3/S6 member at the time, I'm not permitted to say what the group
> did on the presentation of the data, but the ATTC report was public.
>
> TTFN,
> Mark
>
>
>
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